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Stable Isotopes in Aerosols

Our investigations of organic aerosol focus on natural contributions to the atmospheric formation of secondary organic aerosol (SOA). In contrast to primary aerosol, secondary aerosol is not directly emitted from a source but formed in the course of atmospheric chemical processes. Major natural sources of secondary organic aerosol are the volatile organic compounds (VOCs) emitted by terrestrial plants. Our group studies the formation of SOA from biogenic emissions and their influence on air quality and climate.

Key measurement methods deployed are aerosol mass spectrometry (AMS) and isotope mass spectrometry (IRMS). Mainly we use simulation chambers (SAPHIR, SAPHIR-Plus, aerosol chamber) for our studies. Experiments simulate conditions prevalent in the lower troposphere and boundary layer in particular with respect to concentrations of trace gases and oxidants. To facilitate the study of atmospheric oxidation of natural mixtures of VOCs we currently develop a plant climate chamber (PLUS) as natural source of VOCs. The main internal cooperation partners for our studies are the groups: Heterogenous Reactions und "Ecosystem Dynamics – Trace gas exchange".

In field studies we investigate the stable isotope composition of aerosols from source and ambient samples. Goal is to determine the aerosol origin and atmospheric transformation based on the isotopic composition of single organic species. Detailed knowledge of sources and atmospheric processing of aerosol is essential for the development of adequate control measures in the context of air quality regulation.

In cooperation with Aerodyne Inc. we develop a method for the quasi-online aerosol collection (ACM). Concurrent measurements of gas and particle phase concentrations of organic species deploying the ACM allow for the experimental determination of partitioning coefficients, a quantity needed for model predictions of the SOA mass formation.

Isotopic composition from aerosol filter samples is determined compound specific through our coupled gas cromatograph – isotope ratio mass spectrometer (GC-IRMS) systems. Currently we are focusing this analysis on the determination of biomass burning tracers in samples from China and Taiwan.

The group is taking lead positions in the EU funded projects PEGASOS and the Marie Curie initial training network PIMMS. The group is furthermore funded through a Helmholtz Professorship.